Return mewt wrapped instances (#12)

* code style changes * no need to have newObj in the outer scope * moved multiRet outside of the function, no need to redeclare * methods that return arrays, setters and unsetters, and multi return value methods now return mewt wrapped instances * moved constants back to method, array -> string, removed TODO
sdgluck · Mar 28, 2017 · 602dc20 · 602dc20
1 parent 2141c5e
commit 602dc20
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Showing 3 changed files with 88 additions and 20 deletions.
diff --git a/index.js b/index.js
@@ -1,30 +1,51 @@
 /** @returns {Array|Object} */
-module.exports = function mewt (target) {
-  let isA = Array.isArray(target)
-    , multiRet = 'push pop shift unshift'
-    , clone = isA ? v => [].concat(v) : v => Object.assign({}, v)
+function mewt(target) {
+  const multiRet = 'push pop shift unshift'
+  const mutArrMethods = 'reverse sort splice fill copyWithin'
+  const nonMutArrMethods = 'filter map concat slice'
+
+  const isA = Array.isArray(target)
+  const clone = isA ? v => [].concat(v) : v => Object.assign({}, v)
 
-  let override = prop => (...args) => {
-    let cl = clone(target)
-    let res = cl[prop](...args)
-    return multiRet.includes(prop) ? [res, cl] : res
+  const override = prop => (...args) => {
+    const mutMethod = mutArrMethods.includes(prop)
+    const nonMutMethod = nonMutArrMethods.includes(prop)
+
+    const cl = nonMutMethod ? target : clone(target)
+    const res = cl[prop](...args)
+    const wrappedRes = (mutMethod || nonMutMethod) ? mewt(res) : res
+
+    return multiRet.includes(prop) ? [wrappedRes, mewt(cl)] : wrappedRes
   }
 
-  let newObj, api = {
-    $set: (prop, val) => (newObj = clone(target), newObj[prop] = val, newObj),
-    $unset: prop => (newObj = clone(target), delete newObj[prop], newObj)
+  const api = {
+    $set: (prop, val) => {
+      const newObj = clone(target)
+      newObj[prop] = val
+      return mewt(newObj)
+    },
+    $unset: prop => {
+      const newObj = clone(target)
+      delete newObj[prop]
+      return mewt(newObj)
+    }
   }
 
-  if (!isA && typeof target !== 'object')
+  if (!isA && typeof target !== 'object') {
     throw new Error('mewt accepts array or object')
+  }
 
   return new Proxy(target, {
     set: () => {
       throw new Error(`${isA ? 'array' : 'object'} is immutable`)
     },
     get: (_, prop) => {
-      if (api[prop]) return api[prop]
+      if (api[prop]) {
+        return api[prop]
+      }
       return target[prop] && ({}.hasOwnProperty.call(target, prop) ? target[prop] : override(prop))
     }
   })
 }
+
+module.exports = mewt
diff --git a/lib/index.js b/lib/index.js
diff --git a/test.js b/test.js
@@ -3,6 +3,11 @@
 const test = require('tape')
 const mewt = require('./lib')
 
+const createAssertMewt = t => input => {
+  t.equal(typeof input.$set, 'function')
+  t.equal(typeof input.$unset, 'function')
+}
+
 test('exports a function', (t) => {
   t.equal(typeof mewt, 'function')
   t.end()
@@ -14,6 +19,7 @@ test('throws without object or array', (t) => {
 })
 
 test('array', (t) => {
+  const assertMewt = createAssertMewt(t)
   {
     // returns new array
     const a = []
@@ -28,8 +34,7 @@ test('array', (t) => {
   {
     // has $set & $unset
     const a = mewt([])
-    t.equal(typeof a.$set, 'function')
-    t.equal(typeof a.$unset, 'function')
+    assertMewt(a)
   }
   {
     // get own property
@@ -42,27 +47,31 @@ test('array', (t) => {
     const n = a.$set(0, '')
     t.deepEqual(n, [''])
     t.notEqual(a, n)
+    assertMewt(n)
   }
   {
     // $unset
     const a = mewt([''])
     const n = a.$unset(0)
     t.deepEqual(n, [])
     t.notEqual(a, n)
+    assertMewt(n)
   }
   {
     // copyWithin
     const a = mewt([1, 2])
     const n = a.copyWithin(0, 2)
     t.deepEqual(n, [1, 2])
     t.notEqual(a, n)
+    assertMewt(n)
   }
   {
     // fill
     const a = mewt([,])
     const n = a.fill('')
     t.deepEqual(n, [''])
     t.notEqual(a, n)
+    assertMewt(n)
   }
   {
     // pop
@@ -72,6 +81,7 @@ test('array', (t) => {
     t.equal(str, '')
     t.deepEqual(n, [])
     t.notEqual(a, n)
+    assertMewt(n)
   }
   {
     // push
@@ -80,13 +90,15 @@ test('array', (t) => {
     t.equal(1, len)
     t.deepEqual(n, [''])
     t.notEqual(a, n)
+    assertMewt(n)
   }
   {
     // reverse
     const a = mewt([1, 2])
     const n = a.reverse()
     t.deepEqual(n, [2, 1])
     t.notEqual(a, n)
+    assertMewt(n)
   }
   {
     // shift
@@ -95,20 +107,23 @@ test('array', (t) => {
     t.equal(num, 1)
     t.deepEqual(n, [2])
     t.notEqual(a, n)
+    assertMewt(n)
   }
   {
     // sort
     const a = mewt(['c', 'b', 'a'])
     const n = a.sort()
     t.deepEqual(n, ['a', 'b', 'c'])
     t.notEqual(a, n)
+    assertMewt(n)
   }
   {
     // sort
     const a = mewt(['a', 'b', 'c'])
     const n = a.splice(0, 1)
     t.deepEqual(n, ['a'])
     t.notEqual(a, n)
+    assertMewt(n)
   }
   {
     // unshift
@@ -117,11 +132,44 @@ test('array', (t) => {
     t.equal(len, 2)
     t.deepEqual(n, [1, 2])
     t.notEqual(a, n)
+    assertMewt(n)
+  }
+  {
+    // filter
+    const a = mewt([1, 2, 3, 4, 5])
+    const filtered = a.filter(e => e % 2 === 0)
+    t.deepEqual(filtered, [2, 4])
+    assertMewt(filtered)
+  }
+  {
+    // map
+    const a = mewt([1, 2, 3, 4, 5])
+    const transformed = a.map(e => e * 2)
+    t.deepEqual(transformed, [2, 4, 6, 8, 10])
+    assertMewt(transformed)
+  }
+  {
+    // concat
+    const a = mewt([1, 2]).concat([3, 4, 5])
+    t.deepEqual(a, [1, 2, 3, 4, 5])
+    assertMewt(a)
+
+    const b = mewt([5, 4]).concat(mewt([3, 2, 1]))
+    t.deepEqual(b, [5, 4, 3, 2, 1])
+    assertMewt(b)
+  }
+  {
+    // slice
+    const a = mewt([1, 2, 3, 4, 5])
+    const sliced = a.slice(1, 4)
+    t.deepEqual(sliced, [2, 3, 4])
+    assertMewt(sliced)
   }
   t.end()
 })
 
 test('object', (t) => {
+  const assertMewt = createAssertMewt(t)
   {
     // returns new object
     const o = {}
@@ -136,12 +184,11 @@ test('object', (t) => {
   {
     // has $set & $unset
     const o = mewt({})
-    t.equal(typeof o.$set, 'function')
-    t.equal(typeof o.$unset, 'function')
+    assertMewt(o)
   }
   {
     // get own property
-    const o = mewt({album: 'Aladdin Sane'})
+    const o = mewt({ album: 'Aladdin Sane' })
     t.equal(o.album, 'Aladdin Sane')
   }
   {
@@ -154,7 +201,7 @@ test('object', (t) => {
   }
   {
     // $unset
-    const o = mewt({album: 'Heroes'})
+    const o = mewt({ album: 'Heroes' })
     const n = o.$unset('album')
     t.equal(o.album, 'Heroes')
     t.equal(n.album, undefined)